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""" Import Qt in a manner suitable for an IPython kernel.
This is the import used for the `gui=qt` or `pylab=qt` initialization.
Import Priority:
if matplotlib has been imported and doesn't support v2 (<= 1.0.1):
use PyQt4 @v1
Next, ask ETS' QT_API env variable
if QT_API not set:
ask matplotlib via rcParams['backend.qt4']
if it said PyQt:
use PyQt4 @v1
elif it said PySide:
use PySide
else: (matplotlib said nothing)
# this is the default path - nobody told us anything
try:
PyQt @v1
except:
fallback on PySide
else:
use PyQt @v2 or PySide, depending on QT_API
because ETS doesn't work with PyQt @v1.
"""
import os
import sys
matplotlib = sys.modules.get('matplotlib')
if matplotlib and matplotlib.__version__ <= '1.0.1':
# 1.0.1 doesn't support pyside or v2, so stick with PyQt @v1,
# and ignore everything else
from PyQt4 import QtCore, QtGui
else:
# ask QT_API ETS variable *first*
QT_API = os.environ.get('QT_API', None)
if QT_API is None:
# QT_API not set, ask matplotlib if it was imported (e.g. `pylab=qt`)
if matplotlib:
# this rc option has been proposed, but is not yet in matplotlib master
# as of writing.
mpqt = matplotlib.rcParams.get('backend.qt4', None)
else:
mpqt = None
if mpqt is None:
# matplotlib not imported or had nothing to say.
try:
# default to unconfigured PyQt4
from PyQt4 import QtCore, QtGui
except ImportError:
# fallback on PySide
try:
from PySide import QtCore, QtGui
except ImportError:
raise ImportError('Cannot import PySide or PyQt4')
elif mpqt.lower() == 'pyqt4':
# import PyQt4 unconfigured
from PyQt4 import QtCore, QtGui
elif mpqt.lower() == 'pyside':
from PySide import QtCore, QtGui
else:
raise ImportError("unhandled value for backend.qt4 from matplotlib: %r"%mpqt)
else:
# QT_API specified, use PySide or PyQt+v2 API from external.qt
# this means ETS is likely to be used, which requires v2
try:
from IPython.external.qt import QtCore, QtGui
except ValueError as e:
if 'API' in str(e):
# API mismatch, give more meaningful message
raise ImportError("""
Assinging the ETS variable `QT_API=pyqt` implies PyQt's v2 API for
QString and QVariant, but PyQt has already been imported
with v1 APIs. You must unset QT_API to work with PyQt4
in its default mode.
""")
else:
raise
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